A semiconductor memory device having the mismatch cell makes a capacitance difference between a bit line pair relatively large during a read operation using at least one dummy memory cell as a mismatch cell selected together with a corresponding memory cell. A LED light module has a flexible wire configuration allowing freedom of movement when the wearing apparel is worn. The at least one first and the at least one second field sources are oriented relative to each other such that in the field interaction the resulting repelling forces and attractive forces substantially cancel each other out and there is an increase and a decrease in the field strength of at least some of the field sources. The housing is such as: the first part is provided with an inner axial cylindrical portion for retaining radially the at least two parts of the ring, and the second part is provided with an outer axial cylindrical portion surrounding the inner axial cylindrical portion and a projected portion extending radially outwards. In a related method for removing a deposit of plaque from a position along a wall of a blood vessel a magnetic field is applied which has a net direction predominantly orthogonal to the direction of the flow of blood through the vessel.